All subterranean water contains mineral and other chemical substances and compounds which are soluble in the water. Most, if not all, of these substances are introduced in the water, which started as rain or snow, as the water flows in natural underground channels.
The problem with water which flows from, or which is pumped from wells in the ground, is to remove the undesirable elements which are in solution. While the undesirable compounds are in solution, they cannot be reduced or removed by a filtration process. There are only two methods by which the undesirable compounds may be removed. The most common method, especially in large water systems such as municipal water systems, is by chemical treatment in combination with filtration. A second method, of which the referenced U.S. patent is an example, is by a combination of aeration and filtration. The object of the latter method is to convert the undesirable compounds which are in unfilterable solution into either precipitates or colloids which may be removed by subsequent filtration.
For purpose of illustration only, two of the more common objectionable soluble compounds in well water are compounds containing sulphur and iron. Although the presence of such compounds may not be visible in the water, the sulphur compounds produce a most objectionable odor and taste, and the iron compounds produce the severe discoloration which is often observed on fixtures such as sinks, bath tubs, and in the water tanks on toilets.
Ferrous carbonate, FeCO.sub.3, is soluble in carbon dioxide and forms ferrous hydrogen carbonate, Fe(HCO.sub.3).sub.2, which is contained in many ground waters. On contact with air, carbon dioxide is lost and oxidation takes place, precipitating the iron as hydrated ferric oxide. In addition to staining fixtures, the hydrated ferric oxide will also form scale in pipes, and will provide a suitable environment for the growth of Crenothrix and other iron-oxidizing bacteria. The purificiation of such iron bearing water may be effected by suitable aeration and filtration.
One apparatus and method for the aeration and filtration of well water is disclosed in the referenced U.S. patent. the necessary equipment is not unreasonable for large commerical installations where it will be serviced on a regular basis by qualified operating personnel; however, it is too cumbersome and expensive for individual home use such as the household of a farmer, or a suburban family which is not on a public water system in which the water is treated at a central station.